Low temperature quantised conductance effects in InSb/AlInSb heterostructures are reported. The one-dimensional confinement is provided by metal Schottky split-gate structures patterned directly onto the material surface. Extremely low... more
Low temperature quantised conductance effects in InSb/AlInSb heterostructures are reported. The one-dimensional confinement is provided by metal Schottky split-gate structures patterned directly onto the material surface. Extremely low Schottky barrier leakage is demonstrated for these devices, in part due to the air bridge gate arrangement implemented. Up to seven quantised energy subbands are discerned in the conductance of the devices
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We have used a novel, simple technique based on bevel etching, to fabricate samples containing lateral n-i-p junctions in an InSb/InAlSb quantum well. The structure was designed by self-consistent solution of... more
We have used a novel, simple technique based on bevel etching, to fabricate samples containing lateral n-i-p junctions in an InSb/InAlSb quantum well. The structure was designed by self-consistent solution of Schrödinger's and Poisson's equations, and grown by molecular beam epitaxy on a SI GaAs substrate. Current/voltage characteristics were measured as a function of temperature between 10 and 80 K,
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... The authors acknowledge the support of the Strategic Research Panel of the UK MoD and CL Jones, CD Maxey and NE Metcalfe of GEC Marconi Infrared Limited for fabrication of the HgxCdxTe heterostructures. British Crown Copyright (1995).... more
... The authors acknowledge the support of the Strategic Research Panel of the UK MoD and CL Jones, CD Maxey and NE Metcalfe of GEC Marconi Infrared Limited for fabrication of the HgxCdxTe heterostructures. British Crown Copyright (1995). References [1] T. Ashley and CT ...
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Research Interests: Engineering, Physics, Condensed Matter Physics, Materials Science, Monte Carlo Simulation, and 13 moreApplied Physics, Optoelectronics, Mathematical Sciences, Physical sciences, Leakage Current, Temperature Dependence, High performance, Room Temperature, Quantum Well, Impact Ionization, Low Temperature, Field effect transistor, and Indium Antimonide
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The luminescent properties of single InSb quantum wells have been investigated as a function of temperature and incident laser power. A large peak was observed in the photoluminescence, corresponding to emission from the quantum well,... more
The luminescent properties of single InSb quantum wells have been investigated as a function of temperature and incident laser power. A large peak was observed in the photoluminescence, corresponding to emission from the quantum well, which moves to lower energy with increasing temperature and tracks the bulk InSb band gap with a constant energy up-shift of ~50 meV. The integrated
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... R, Whitehouse, CF McCcnvilìe, AG CuElis, T. Ashley, SJ Courtney, and С. T. Elliott Roya! ... Detailed secondary-ion mass spectrometry measurements also demonstrate that there is no large-scale interdifiusion of constituent elements at... more
... R, Whitehouse, CF McCcnvilìe, AG CuElis, T. Ashley, SJ Courtney, and С. T. Elliott Roya! ... Detailed secondary-ion mass spectrometry measurements also demonstrate that there is no large-scale interdifiusion of constituent elements at the interface. ...
Research Interests: Engineering, Physics, Materials Science, Chemistry, Electron Microscopy, and 15 moreSecondary Ion Mass Spectrometry, Applied Physics, Electron Diffraction, Molecular beam epitaxy, Optoelectronics, High Resolution Transmission Electron Microscopy, Physical sciences, Nucleation, Dislocations, Room Temperature, Electrical Properties, Science Technology, Epitaxy, Gallium Arsenide, and Large Scale
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High-performance InSb diode junctions have been grown for the first time by molecular-beam epitaxy. Without any optimization of the device parameters, such as doping levels, the detectors exhibit a limiting D-asterisk(lambda p k) of 3 x... more
High-performance InSb diode junctions have been grown for the first time by molecular-beam epitaxy. Without any optimization of the device parameters, such as doping levels, the detectors exhibit a limiting D-asterisk(lambda p k) of 3 x 10 to the 12th cm-Hz exp 1/2/W. This permits BLIP operation in a background flux as low as 10 to the 13th photons/sq cm/s. When the ambient scene temperature is 295 K, for example, BLIP operation is obtained for cold shield apertures corresponding to f/numbers greater than 20.
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ABSTRACT Using an FTIR-based photo-modulated transmission spectroscopic technique a red-shift in bandgap has been observed at room temperature for an InSb1-xNx ternary alloy, relative to binary InSb, and determined to be approximately... more
ABSTRACT Using an FTIR-based photo-modulated transmission spectroscopic technique a red-shift in bandgap has been observed at room temperature for an InSb1-xNx ternary alloy, relative to binary InSb, and determined to be approximately around 16meV (10%), corresponding to an incorporated nitrogen concentration of 0.1%.
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InSb-based quantum well field-effect transistors, with gate length down to 0.2 μm, are fabricated for the first time. Hall measurements show that room temperature electron mobilities over 30,000 cm 2V-1s-1 are achieved with a sheet... more
InSb-based quantum well field-effect transistors, with gate length down to 0.2 μm, are fabricated for the first time. Hall measurements show that room temperature electron mobilities over 30,000 cm 2V-1s-1 are achieved with a sheet carrier density over 1×1012 cm-2 in a modulation doped InSb quantum well with AlxIn1-xSb barrier layers. Devices with 0.2 μm gate length and 20% Al
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The spectral properties of InSb/AlxIn1−xSb quantum-well light-emitting diodes have been investigated at T = 15K in a magnetic field of approximately 250mT, applied by mounting the diodes inside a toroidal permanent magnet. In all cases,... more
The spectral properties of InSb/AlxIn1−xSb quantum-well light-emitting diodes have been investigated at T = 15K in a magnetic field of approximately 250mT, applied by mounting the diodes inside a toroidal permanent magnet. In all cases, the low energy side of the spectra is shifted towards higher energy with the field applied.
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We study four compressively strained GaInSb/AlGaInSb type I multi quantum-well (QW) laser structures grown on GaAs, with increasingly strained QWs, aimed at emitting at ~4mum. This wavelength region is highly important for applications... more
We study four compressively strained GaInSb/AlGaInSb type I multi quantum-well (QW) laser structures grown on GaAs, with increasingly strained QWs, aimed at emitting at ~4mum. This wavelength region is highly important for applications such a free space communication, biomedical imaging and trace gas sensing. The structures are analysed using photoluminescence, photo-modulated reflectance and, at room temperature, using our novel, recently
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Indium antimonide (InSb) has the highest electron mobility and saturation velocity of any conventional semiconductor, giving potential for a range of analogue and digital ultra-high speed, low power dissipation applications. N-channel... more
Indium antimonide (InSb) has the highest electron mobility and saturation velocity of any conventional semiconductor, giving potential for a range of analogue and digital ultra-high speed, low power dissipation applications. N-channel quantum well FETs have been fabricated with current gain cut-off frequency (fT) of more than 250 GHz and power gain cut-off frequency (fmax) of 500 GHz. Outline designs confirm
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Indium antimonide has the highest electron mobility and saturation velocity of any semiconductor, so has potential for ultra-high frequency operation with very low power dissipation. Unoptimised, uncooled quantum well heterojunction FETs,... more
Indium antimonide has the highest electron mobility and saturation velocity of any semiconductor, so has potential for ultra-high frequency operation with very low power dissipation. Unoptimised, uncooled quantum well heterojunction FETs, with gate length of 85nm, that have a cutoff frequency of 340GHz at only 0.5 V Vds. The prospects of this technology for future microwave applications in excess of
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The application of non-equilibrium transport techniques to Molecular Beam Epitaxy (MBE) grown InSb/InAlSb heterostructure diodes has produced practical devices such as midinfrared LED's and negative luminescent sources that operate at... more
The application of non-equilibrium transport techniques to Molecular Beam Epitaxy (MBE) grown InSb/InAlSb heterostructure diodes has produced practical devices such as midinfrared LED's and negative luminescent sources that operate at room temperature. By extending the epitaxial growth to vicinal InSb substrates it has been demonstrated that the temperature window for high quality epitaxy can be lowered by ∼12°C, giving greatly improved epilayer morphology. The degree of misorientation needed for given growth temperatures is shown from Atomic Force Microscope (AFM) measurements to be only ∼2°. In addition, the lower growth temperature gives improved dopant activation, lower trap densities and lower reverse bias leakage currents, with consequent benefits to device performance.
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Three GaInSb/AlGaInSb type I multi-quantum-well (QW) laser structures grown on GaAs, with increasingly strained QWs, aimed at emitting at ~4 µm, are analysed using our Fourier transform infrared surface photo-voltage spectroscopy... more
Three GaInSb/AlGaInSb type I multi-quantum-well (QW) laser structures grown on GaAs, with increasingly strained QWs, aimed at emitting at ~4 µm, are analysed using our Fourier transform infrared surface photo-voltage spectroscopy technique. The measurements clearly yield a full set of transitions including not only the barrier bandgap, but also the QW ground state transition, from which the device operating wavelengths can be inferred, and up to five excited state QW transitions. The full set of measured transition energies are then compared closely with those predicted by an 8-band k sdot p model which gives a generally good agreement for the QW transitions, but an indication that the current literature values for the AlGaInSb bandgap seem to be in considerable error for the present alloy compositions.
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... 1 t @kg tanh 2 tanh & tanh& f O k tanhk Jn = @qnu L S387 Page 4. T Ashley et al ... The dif-ferent contributions as functions of acceptor doping are shown in figure 2 for aharrier with an energy gap three times that of... more
... 1 t @kg tanh 2 tanh & tanh& f O k tanhk Jn = @qnu L S387 Page 4. T Ashley et al ... The dif-ferent contributions as functions of acceptor doping are shown in figure 2 for aharrier with an energy gap three times that of the bulk material. ...
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... PC Findlay, CR Pidgeon, H Pellemans¶, R Kotitschke, BN Murdin, T Ashley§, AD Johnson§, AM White§ and CT Elliott§ ... The procedure uses a knowledge of the non-parabolic so-called Kane band structure (see below), which determines... more
... PC Findlay, CR Pidgeon, H Pellemans¶, R Kotitschke, BN Murdin, T Ashley§, AD Johnson§, AM White§ and CT Elliott§ ... The procedure uses a knowledge of the non-parabolic so-called Kane band structure (see below), which determines the (final and initial) electron and ...
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ABSTRACT We present high-field magnetotransport data from a range of 30-nm-wide InSb/InAlSb quantum wells with room-temperature mobilities in excess of 6 m2 V−1 s−1. Samples with the narrowest Landau level broadening exhibit beating... more
ABSTRACT We present high-field magnetotransport data from a range of 30-nm-wide InSb/InAlSb quantum wells with room-temperature mobilities in excess of 6 m2 V−1 s−1. Samples with the narrowest Landau level broadening exhibit beating patterns in the magnetoresistance attributed to zero-field spin splitting. Rashba parameters are extracted from a range of samples and gate biases using the difference in spin populations inferred from fast Fourier transforms of the data. The influence of Landau level broadening and spin-dependent scattering rates are investigated by magnetoconductance simulations, which provide key signatures that we were able to verify by experimental observation. These results demonstrate that in addition to the large Zeeman splitting, the combination of large and spin-dependent broadening is the significant parameter in controlling the appearance of beating in these structures.
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Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a 'source'of IR... more
Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a 'source'of IR radiation for gas sensing; radiation ...
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The addition of small amounts of nitrogen to III–V semiconductors leads to a large degree of band gap bowing, giving rise to band-gaps smaller than in the associated binary materials. The incorporation of active nitrogen has been... more
The addition of small amounts of nitrogen to III–V semiconductors leads to a large degree of band gap bowing, giving rise to band-gaps smaller than in the associated binary materials. The incorporation of active nitrogen has been previously demonstrated for InNxSb1−x (x⩽0.7%) and GaNxSb1−x (x⩽1.75%) material; however, the as-grown carrier concentrations precluded incorporation into a device structure. Here we report the reduction in the as-grown carrier concentration in InNSb by annealing, whilst retaining the active nitrogen content. FTIR absorption measurements show the first direct experimental evidence of narrowing of the InSb bandgap due to nitrogen incorporation. As an alternative route to defect reduction and device compatible material we report on the growth of Ga1−yInyNxSb1−x with 0⩽y⩽30% and x=1.6±0.2% and demonstrate near lattice matching of the material to GaSb.
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Accurate determination of trap density in the active region of mid-infrared narrow-bandgap detectors is crucial in the development towards background-limited performance at higher operating temperatures. We have used both optical and... more
Accurate determination of trap density in the active region of mid-infrared narrow-bandgap detectors is crucial in the development towards background-limited performance at higher operating temperatures. We have used both optical and electrical measurements to determine the trap density in InSb/InAlSb nonequilibrium detector structures. Both of these techniques result in very good agreement with trap densities of 5×1014 cm-3.
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The application of electron spectroscopies in dilute nitride semiconductor research for both chemical analysis and the determination of electronic and lattice vibrational properties is described. X-ray photoelectron spectroscopy of the... more
The application of electron spectroscopies in dilute nitride semiconductor research for both chemical analysis and the determination of electronic and lattice vibrational properties is described. X-ray photoelectron spectroscopy of the nitrogen bonding configurations in dilute InNxSb1-x and InNxAs1-x alloys is presented. High resolution electron-energy-loss spectroscopy (HREELS) of the plasmon excitations in InNxSb1-x is shown to provide information on the electronic
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... 1 Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB, UK 2 QinetiQ, Malvern Technology Centre, Malvern WR14 3PS, UK E-mail: jon.pugh@bristol. ac.uk and m.cryan@bristol.ac.uk ... J. Opt. A: Pure... more
... 1 Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB, UK 2 QinetiQ, Malvern Technology Centre, Malvern WR14 3PS, UK E-mail: jon.pugh@bristol. ac.uk and m.cryan@bristol.ac.uk ... J. Opt. A: Pure Appl. Opt. 11 (2009) 054006 JR Pugh et al ...